Plasma display panels (hereinafter will be referred to as PDPs) have become widespread as display devices of which representatives are thin-screen televisions. PDPs are display devices capable of thin and large screen display. The volume of production of PDPs is increasing by leaps and bounds year by year like liquid crystal display panels. A large number of technical literature documents have already been published concerning the display technology for plasma display devices using such PDPs (see non-patent document 1 for example).
Since such a plasma display device utilizes plasma discharge to display an image, the temperature of the PDP thereof is likely to become high. In addition, the control circuit for controlling the image display operation of the PDP includes a number of electronic components that generate heat. Accordingly, the temperature within the casing of such a plasma display device is likely to be elevated. For this reason, the plasma display device is provided with appropriate heat dissipation measures.
For example, FIG. 11 shows one exemplary construction of a conventional plasma display device using a PDP as a display device. Specifically, FIG. 11(a) is a rear view showing the plasma display device (in a condition without a back cover 18 to be described later) as viewed from behind and FIG. 11(b) is a sectional view, taken along line VB-VB of FIG. 11(a), of the plasma display device.
As shown in FIG. 11, a rectangular PDP 111 has a rear joined and fixed to a rectangular chassis 12 (i.e., a back member) having a slightly larger area than the PDP 11. The chassis 12 in a condition fixed to the PDP 111 is secured to a leg portion 13 serving as a pedestal of the plasma display device 150.
A front cover 15, which is positioned on the front of the PDP 11, has an opening matching a display surface of the PDP 11. A protective panel 14 is mounted on the front cover 15 so as to fit the opening.
On the rear of the chassis 12, a circuit board 17 carrying various electronic components 16 (including a driver LSI for example) mounted thereon for driving the PDP 11 is fixed to the chassis 12 as spaced a fixed clearance from the rear surface of the chassis 12 by means of a spacer S.
A back cover 18 is mounted on the leg portion 13 so as to embrace the PDP 11, the chassis 12, the electronic components 16 and the circuit board 17 from behind. The front cover 15 is fitted on a front portion of this back cover 10.
The back cover 18 is provided at suitable portions thereof with plural air intake holes 19a, 19b and 19c for allowing air to flow into the plasma display device 150 therethrough and plural air exhaust holes 19d and 19e for exhausting air exteriorly of the plasma display device 150.
As compared with other displays such as a liquid crystal display panel and a cathode-ray tube, the PDP 11 is likely to be heated to elevated temperatures due to image display relying upon discharge light emission. Since the PDP 11 uses a higher driving voltage than other displays (driving voltage: 200 to 300 V), the electronic components 16 (including the driver LSI for example) mounted on the circuit board 17 are also likely to be heated to elevated temperatures. Further, there is a tendency to raise the driving voltage for the driver LSI in order to raise the luminous efficiency of the PDP 11. This tendency makes the thermal problem of the plasma display device 160 more noticeable.
As shown in FIG. 11, a plurality of rod-shaped heat transfer members 20a and 20b are provided in order to allow heat generated from the PDP 11 and the electronic components 16 to dissipate to the back cover 18 efficiently. Each of the heat transfer members 20a and 20b has one end brought into contact with at least one of the PDP 11 via the chassis 12 and the circuit board 17 (into contact with the PDP 11 in FIG. 11) and an opposite end brought into contact with the back cover 18.
Thus, the rod-shaped heat transfer members 20a and 20b are positioned to allow heat transfer to occur between the back cover 18 and at least one of the PDP 11 and the circuit board 17.
Such rod-shaped heat transfer members 20a and 20b are evenly distributed in the lower and upper halves of the back cover 18 as shown in the plan view at FIG. 11(a). When the back cover 18 is equally divided into the upper half and the lower half, three rod-shaped heat transfer members 20a interconnecting the back cover 18 and the PDP 11 are arranged side by side horizontally of the plasma display device 150 in the upper half of the back cover 18. Similarly, three rod-shaped heat transfer members 20b interconnecting the back cover 18 and the PDP 11 are arranged side by side horizontally of the plasma display device 150 in the lower half of the back cover 18.
A structure achieving an effect similar to the heat dissipation effect of such rod-shaped heat transfer members 20a and 20b has already been published (see patent document 1). According to the design for heat dissipation described in this patent document 1, an electronic component that is likely to be heated to elevated temperatures and a rear portion of a casing are interconnected by a heat transfer member, so that heat generated from the electronic component is allowed to be transferred to the rear portion of the casing through the heat transfer member and then dissipated externally. Therefore, such a structure is capable of inhibiting an elevation in the temperature within the casing.
In attempt to minimize the elevation in the temperature within the casing of the plasma display device due to long-time display operation of the PDP, various heat dissipation techniques for the plasma display device have been developed hitherto.
For example, a plasma display device, which is intended to efficiently suppress localized heat generation by the PDP, has been disclosed, wherein: a heat-conductive sheet comprising silicone rubber or the like is interposed between the PDP and a heat-conductive plate of aluminum in order to improve the heat transfer coefficient between the PDP and the heat-conductive plate thereby enhancing the thermal intimacy therebetween; and plural heat pipes, radiator fins and a heat dissipation fan are disposed above the heat-conductive plate (see patent document 2).
Also, a cooling structure for plasma displays has been disclosed wherein a radiator joined to a PDP-supporting chassis and to an electronic component is joined to a rear cover having a high thermal conductivity which comprises an aluminum plate for example, thereby making it possible to dissipate heat generated from the PDP and the electronic component to the rear cover efficiently (see patent document 3).
Further, a PDP rear frame which has its weight kept light and is excellent in strength and heat dissipation property has been obtained by forming a linear ridge-groove structure on an internal surface of a PDP rear frame having an excellent thermal conductivity (comprising an aluminum plate for example) (see Patent document 4).
Non-patent document 1: FLAT PANEL DISPLAY 1999 (NIKKEI MICRODEVICES)
Patent document 1: Japanese Patent Laid-Open Publication No. 2000-338904
Patent document 2: Japanese Patent Laid-Open Publication No. HEI 11-251777
Patent document 3: Japanese Patent Laid-Open Publication No. 2000-347578
Patent document 4: Japanese Patent Laid-Open Publication No. 2001-242792